Mendes was the 1998 CAA Rookie of the Year, and a two-time NSCAA United Soccer Coaches Association All-Region selection.
Mendes started his career with the Long Island Rough Riders of the USL Pro Soccer League in 2002.
Mendes signed with the MetroStars before the start of the 2005 season, and became the starter in central defense, filling the position formerly held by Eddie Pope.
Mendes continued his solid play anchoring the clubs backline during the early part of the 2007 season with New York Red Bulls.
On November 30, 2011, the Red Bulls declined the 2012 option on Mendes's contract, making him eligible for the 2011 MLS Re-Entry Draft.
[11] On April 13, 2014, Mendes scored the first two goals of his professional career in a 4–0 victory over the Atlanta Silverbacks, earning him NASL Player of the Week honors.
Mendes was inducted into the Long Island Soccer Football League's inaugural hall of fame class on November 22, 2015.
The Cosmos went on hiatus in January 2021, and Mendes spent one season an assistant coach for Queens College before joining the staff of the U.S.